1. Field of the Invention
The present invention relates to a gauge head for a Quadrupole mass spectrometer with an ion source, a one-piece Quadrupole separating system, a detector, a flange for attachment of the gauge head to a vacuum chamber and carrying parts for these components.
2. Description of the Related Art
A gauge head of this type is disclosed in the publication "Grundlagen der Vakuumtechnik, Berechnungen and Tabellen" published by Leybold-Heraeus GmbH, FRG, Edition 11/82, pages 58 and 59. The Quadrupole separating system consists of a one-piece cylindrical ceramic part with a paraxial opening. The cross section of this opening has the shape of four hyperbolic branches arranged symmetrically about the cylinder axis. The hyperbolically shaped surfaces are furnished with metal coatings, forming four electrodes with a hyperbolic cross section. A high frequency voltage with superimposed DC component is applied to these electrodes. Depending on the magnitude of these voltages an ion having the mass number M may pass or not pass the separating system. Quadrupole separating systems of this kind are disclosed in German Patent Applications, publication Nos. 22 15 763, 23 47 544 and 26 25 660.
A state of the art quadrupole gauge head requires a main carrier, made of metal with numerous current feedthroughs. Attached to this carrier is the flange which is used to attach the gauge head to a matching flange on the vacuum chamber. The wires leading through the carrier are terminated by a system of connectors at the outside of the flange, to which supply voltages and signal processing components are connected. Detector and Quadrupole separating system are held in place inside the flange by the main carrier. Moreover, a tube which surrounds the separating system is provided by the carrier. This tube carries the ion source anterior to the separating system.
The design of the aforementioned Quadrupole gauge head is costly and complex. Due to the numerous components which have to be aligned with respect to each other, time and effort spent for assembly of the gauge head is considerable. The aforementioned gauge head is highly sensitive to shocks and vibrations. The number of its components is high and subsequently the area of these components exposed to the vacuum of the vacuum chamber is large, impairing the generation of the vacuum required for operation of the mass spectrometer.